Glycogen: What it is, Why it’s important

Sam Bassetti races on the Herbalife 24 p/b Marc Pro-Nature’s Bakery Elite Cycling Team and is excited to leverage his experience and educational background to help you become a better cyclist. In this article Sam gives us an introduction to glycogen.

You may have heard your riding buddies mumbling something about replacing glycogen stores while stuffing their face with a “personal” sized pizza post ride. So what is glycogen and why is it important? Here I will give a brief introduction on the topic.

First, it’s important to understand the relationship between carbohydrates, glucose and glycogen.

Carbohydrates

Carbohydrates can also be referred to as saccharides and are a group of organic molecules that includes sugars, starches and cellulose (1). They can be made up of multiple saccharide molecules linked together (polysaccharides), two saccharide molecules (disaccharides) or a single saccharide molecule (monosaccharide).

Glucose

Monosaccharides and disaccharides can also be referred to as sugars. Glucose (blood sugar) is an important monosaccharide that provides energy for muscle contractions (1). Glucose is stored as a specific polysaccharide in our bodies called glycogen.

Glycogen

Many molecules of Glucose are chained together to form glycogen, which is stored in our muscles and liver (1). Glycogen is broken down into individual glucose molecules in muscle cells when needed for energy production.

Glycogen is essentially stored carbohydrate, and as we know carbohydrate as a substrate for endurance exercise is very important. Glycogen is mainly stored in our muscle fibers and liver (1) and is readily available for use during exercise.

A few landmark early studies have set the stage for why glycogen is so important. These studies showed that:

Work time to exhaustion was directly related to starting glycogen stores in muscles used (3).

These results have been confirmed by many related studies (4,11,12). It is clear that glycogen is important, and the amount of glycogen that you have is also important.

A normal, healthy 70kg male eating a high carbohydrate diet might have around 600g (2,400 calories) of carbohydrate stored as glycogen in their muscles, plus another 90g in the liver (5,6,7). Compare this to about 10g of carbohydrate in the blood stream (5,6,7), and you can quickly see why glycogen is vital as a source of carbohydrate during exercise.

Glycogen before exercise

A high carbohydrate diet is key to maintaining and maximizing glycogen stores (5,6,7). This is pretty straightforward, in order to store carbohydrates, you need to first eat carbohydrates.

There are some slightly more complex strategies to maximizing your glycogen stores such as carbo-loading or carbohydrate periodization that involve altering your carbohydrate intake in specific ways, but a more simple strategy will be easier to follow.

Glycogen during exercise

Once you start riding or racing, you will be using up your glycogen stores, especially during the first hour of exercise and during higher intensity efforts (1). You will not be replacing glycogen stores as you ride, but rather increasingly relying on blood glucose and free fatty acids in the later stages of a longer ride or race (10).

Again, see Are you Fueling Enough on the Bike? for detailed nutritional recommendations, but understand that once you have started exercising, the glycogen you started with is all you have to work with, additional carbohydrate needs will need to be met with on the bike nutrition.

Glycogen after exercise

Replacing glycogen stores should be one of your main concerns immediately post ride or race:

Chronic depletion of glycogen has been shown to be detrimental to performance during heavy training (9).

The rate of glycogen replacement is highest immediately following exercise upon ingesting a high carbohydrate meal (8).

Glycogen levels should return to normal levels in about 24 hours if you eat a carbohydrate rich meal post ride, and continue to ingest high levels of carbohydrates in your other meals (8).

In order to ensure that your glycogen stores return to normal levels for your next workout, eat a high carbohydrate meal immediately post exercise, and continue to eat carbohydrates as a part of your normal meals.

Summary

Glycogen is stored carbohydrate, and is mainly present in our muscles (1,5,6,7).

Share This

Related

Sam has been racing at the Junior, U23, Elite and Professional levels in the U.S. and Internationally since 2009. Relying on his experience and his degree in Exercise Biology, he currently coaches and trains cyclists for Data Drive Athlete and the Team Swift Junior Development Team out of Santa Rosa, CA. He currently races at the professional level with the Elevate KHS Pro Cycling in the US and around the globe.